Swap image with check/uncheck of Radio Button

[lemat]

Hi,
I use a radio button form in which users can select a color by clicking
on a image.
I would like this image to change to another one when it's chosen.
(image with a "Chosen" Stamp in the middle)
Of course I like it to be restored if hte user select another color.

I've tried to add behaviour to the image (swap on click) and on the
button (onchange swap restore) but it doesn't work (hte image id
swapped and restored almost instantly).

Any ideas ?

Mathieu